I wonder if there is a course in high school or college about email? I remember this subject in high school (it may have been a quarter focus in English). Those of us, past the days of formal education, have just discovered our own equilibrium on how to compose and reply to emails.
My current pet peeve is those people who constantly hit "reply all".
Think about the "reply all" feature - only email technology has recently allowed this capability. Group discussions were relegated to committee meetings and even then only a few participants (the vocal ones) participated. There is always one person in the committee meeting that "needs to be heard" - call him (or her) the actor of the group.
I rarely use the reply all button when responding to an email. It clutters my email when I receive them and provides little added value in information.
So don't be the guy in the committee that wants to hear himself speak- skip the reply all button.